What is the recommended dosage of Sulfatrim (trimethoprim/sulfamethoxazole) for pediatric patients?

Sulfatrim Pediatric Dosage

For most pediatric infections in children over 2 months of age, administer 8-12 mg/kg/day of trimethoprim (40-60 mg/kg/day of sulfamethoxazole) divided into 2 doses every 12 hours. 1, 2

Age-Based Contraindication

• Never administer Sulfatrim to infants under 2 months of age due to the risk of kernicterus 1, 3

Standard Dosing by Indication

Skin and Soft Tissue Infections (including MRSA)

• 8-12 mg/kg/day of trimethoprim divided into 2 doses for 7-10 days 1, 2

Urinary Tract Infections

• 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, divided every 12 hours for 10 days 3
• Alternative regimen: 4 mg/kg trimethoprim (20 mg/kg sulfamethoxazole) twice daily for 5 days 1

Shigellosis

• 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, divided every 12 hours for 5 days 3

Acute Otitis Media

• 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, divided every 12 hours for 10 days 3

Pneumocystis jirovecii Pneumonia (PCP)

Treatment:

• 15-20 mg/kg/day of trimethoprim (75-100 mg/kg/day of sulfamethoxazole) divided into 3-4 doses for 14-21 days 2, 3

Prophylaxis:

• 150 mg/m² trimethoprim and 750 mg/m² sulfamethoxazole daily, divided twice daily, given 3 consecutive days per week 4, 3
• Alternative: 8 mg/kg/day of trimethoprim divided into two doses 2
• Maximum daily dose should not exceed 1600 mg sulfamethoxazole and 320 mg trimethoprim 3

Pertussis Prophylaxis

• 8 mg/kg/day trimethoprim (40 mg/kg/day sulfamethoxazole) for 14 days for all household and close contacts 1

Weight-Based Tablet Dosing Guide

For standard infections (every 12 hours): 3

• 22 lb (10 kg): 1 tablet (400 mg/80 mg)
• 44 lb (20 kg): 1 tablet (400 mg/80 mg)
• 66 lb (30 kg): 1½ tablets (400 mg/80 mg)
• 88 lb (40 kg): 2 tablets (400 mg/80 mg) or 1 double-strength tablet

Renal Dose Adjustment

When renal function is impaired: 3

• Creatinine clearance >30 mL/min: Use standard dosing
• Creatinine clearance 15-30 mL/min: Use half the usual regimen
• Creatinine clearance <15 mL/min: Do not use

Mandatory Monitoring Requirements

• Obtain complete blood count with differential and platelet count at treatment initiation 1, 2
• Repeat monthly during prolonged therapy to detect neutropenia, thrombocytopenia, and anemia 1, 2
• Adverse reactions occur in approximately 15% of HIV-infected children 1, 2

Adverse Effects Management

Mild to moderate rash:

• Temporarily discontinue treatment and restart when resolved 1, 2

Urticarial rash or Stevens-Johnson syndrome:

• Permanently discontinue treatment 1, 2

Critical Contraindications and Precautions

• Absolute contraindication: Age <2 months 1, 3
• Absolute contraindication: Known hypersensitivity to sulfonamides or trimethoprim 1
• Use extreme caution in G6PD deficiency due to hemolytic anemia risk 1, 2, 4
• Use caution in hepatic insufficiency 1, 2
• Use caution in renal insufficiency with appropriate dose adjustment 1

Important Drug Interactions

• Avoid concurrent use with methotrexate at treatment doses due to severe bone marrow suppression risk 4
• Use caution with anticoagulants, hypoglycemics, thiazide diuretics, and anticonvulsants 1

Common Pitfalls to Avoid

• Do not use in neonates or infants under 2 months—kernicterus risk is absolute 1, 3
• Do not forget to adjust dosing in renal impairment—drug accumulation causes toxicity 3
• Do not skip baseline and monthly CBC monitoring during prolonged therapy—hematologic toxicity is common 1, 2
• Do not ignore mild rash—temporarily stop and reassess rather than continuing through potential Stevens-Johnson syndrome 1, 2